Look up the Oregon Treaty and the Anglo American Treaty of 1818. The US purchased the Oregon territory which at the time made up a huge chunk of former British land. The US also won significant amounts of land in the Alaskan Border dispute of 1905

Except Canada was a British colony up until 1867, where they were given internal governing power, and wasn't even a full soveriegn nation until 1982. In which BRITAIN was the one that decided the outcome when they sided with the US in the Alaskan border dispute. This took place AFTER 1867, which only proves further that the British had full control of your country up until 1982. So, you get your **** together